Dermal penetration enhancers and drug delivery systems involving same

ABSTRACT

A transdermal drug delivery system which comprises at least one physiologically active agent or prodrug thereof and at least one dermal penetration enhancer; characterised in that the dermal penetration enhancer is a safe skin-tolerant ester sunscreen. 
     A non-occlusive, percutaneous or transdermal drug delivery system which comprises: 
     (i) an effective amount of at least one physiologically active agent or prodrug thereof; 
     (ii) at least one non-volatile dermal penetration enhancer; and 
     (iii) at least one volatile liquid; 
     characterised in that 
     the dermal penetration enhancer is adapted to transport the physiologically active agent across a dermal surface or mucosal membrane of an animal, including a human, when the volatile liquid evaporates, to form a reservoir or depot of a mixture comprising the penetration enhancer and the physiologically active agent or prodrug within said surface or membrane; 
     and the dermal penetration enhancer is of low toxicity to, and is tolerated by, the dermal surface or mucosal membrane of the animal.

This is a divisional application of U.S. Ser. No. 09/125,436, filed Dec.18, 1998, which is a national phase of PCT/AU97/00091 filed Feb. 19,1997.

The present invention relates to percutaneous or transdermal drugdelivery. More specifically, the invention relates to a topicalabsorption/penetration enhancing agent for use in the delivery of aphysiologically active agent to an animal, including a human. Theinvention also relates to a system for the non-occlusive delivery to ananimal of a physiologically active agent across a dermal surface ormucosal membrane of the animal. Transdermal drug formulations of thepresent invention may be used for local application or systemicdelivery.

The prevention or treatment of local or topical disease states orconditions of the skin has traditionally used simple non-occlusivedelivery systems. These drug delivery systems usually include a volatileand/or non-volatile medium whereby a composition of the drug and mediumis topically applied to the skin, generally in the vicinity of ordirectly on the area of skin to be treated. Such delivery systemsusually take the form of emulsions, creams, ointments, foams, gels,liquids, sprays and aerosols. These delivery systems are generally usedto treat skin inflammations, soft-tissue contusions, parasites, fungaland bacterial topical infection and topical analgesia. The limitationwith this type of delivery system is that systemic drugs are generallynot suitable for this type of administration. Some major problems withthe current state of the art relate to a lack of efficacy of systemicdrugs because of the low drug flux across the skin, as observed fordrugs such as testosterone, amlodipine, fentanyl, buprenorphine and manyothers. Other drugs, such as glyceryl trinitrate, Nitrobid™ (a drug forthe treatment of angina), are difficult to deliver by these systems dueto the inability to adequately control the rate of drug delivery, or therequirement for a very large application area. Other problems with thepoor dermal penetration of drugs is that the drug can be easily washedoff or transferred to clothes, other surfaces or other animals.

The dermal delivery of drugs may represent the oldest form of drugdelivery in human history. Resins and animal fats were probably used byhumans in early times to treat damage to the skin resulting frominjuries and burns. Such substances for local delivery of activesubstances remained largely unchanged until as late as this century. Theconcept of transdermal systemic drug delivery was first seriouslyadvocated by Dr Alejandro Zaffaroni in U.S. Pat. Nos. 3,598,122,3,731,683 and 3,797,494 from the early 1970s. Transdermal systemic drugdelivery provides an effective method of achieving improvedbioavailability for physiologically active substances where the drugsare poorly absorbed by traditional routes of delivery. It can also beused where oral dosing is poorly tolerated or not possible.

Transdermal formulations are however limited. For example polar drugstend to penetrate the skin too slowly. Since most drugs are of a polarnature this limitation is significant, as is the fact that many drugscause irritation at the site of topical application.

Two main methods are known for assisting the rate of penetration ofdrugs across the skin. The first is to increase the thermodynamicactivity of the drug. The thermodynamic activity of a drug in a dermalformulation is proportional to the concentration of the drug and theselection of the vehicle. According to the laws of thermodynamics, themaximum activity of a drug is related to that of the pure drug crystal.The second method involves the use of compounds known as penetrationenhancers to increase the permeability of the dermal surface and hasgenerally proven to be more convenient and effective.

Since the early 1970s the main focus of transdermal systemic drugdelivery has been, and still is, on transdermal patch devices. Thesepatch devices are like bandages which are attached to the surface ofintact skin for prolonged periods of time to allow a desired systemicdelivery of a drug or other physiologically active agent. Thesetransdermal patch devices occlude the skin and trap the drug, togetherwith volatiles and vehicle excipients, between the skin and an outerimpermeable backing membrane. The membrane prevents the evaporation ordiffusion of vehicle excipients, volatiles and drug into an environmentother than the target skin site. The prolonged length of time requiredfor transfer of the drug and excipients from the patch into the skin canand often does result in local skin irritation. The irritation is causedby prolonged contact on the skin by the drug, volatiles, vehicleexcipients, or the adhesive used to attach the patch device to the skin.The occlusive nature of the patch device also restricts the naturalability of the skin to “breathe”, increasing the risk of irritation.With added problems of complex and costly manufacturing processes fortransdermal patch devices there is a need for improved transdermal drugdelivery systems.

The rate of drug delivery across a dermal surface can be increased bydermal penetration enhancers. The problem with most known dermalpenetration enhancers is that they are often toxic, irritating orallergenic. These enhancers tend to be proton accepting solvents such asdimethylsulfoxide and dimethyacetamide. More recently, 2-pyrrolidine,N,N-diethyl-m-toluamide (Deet), 1-dodecal-azacycloheptane-2-one(Azone®), N,N-dimethylformamide, N-methyl-2-pyrrolidine and calciumthioglycolate have been reported as effective enhancers. However,difficulties remain with such dermal enhancers because the problem ofirritation at the site of application has not been overcome.

The most critical problem with these compounds however is theirtoxicity. If a compound when used as a dermal enhancer is toxic,irritating or allergenic, then that compound is unsuitable forapplication to the animal body. Dimethyl sulfoxide and dimethylacetamide are not clinically acceptable for these reasons. Although Deetand Azone® have lower reported toxicities, their toxicity is still suchthat they are not widely used. It is possible that Azone® may beemployed as a dermal penetration enhancer if the amount applied issufficiently small so as not to be appreciably toxic, irritating orallergenic to the animal.

The thermodynamic activity of a drug can be increased by employingsupersaturated systems which give rise to unusually high thermodynamicpotentials [Coldman, et al., J. Pharm. Sci., 58(9), 119, 1969]. However,topical vehicles relying on supersaturation, have the major limitationof formulation instability, both prior to and during application to theskin. As such, they are of limited clinical value within a non-occlusivevolatile:non-volatile delivery vehicle, because as soon as theformulation comes into contact with a person's clothing or the like, thedrug often precipitates; hence the formulation is no longersupersaturated and any enhanced percutaneous absorption ceases.

Other workers such as Kondo, et al., [J. Pharmacobio-Dyn., 10, 743,1987] who were using supersaturation to achieve enhanced transdermaldrug delivery, have relied on the use of anti-nucleating polymers tostabilize the formulation. However, the applied drug formulationsstabilised with polymers formed an appreciable surface mass on the skinwhich remained there over a prolonged duration of many hours, not a fewminutes. So while Kondo advocated the use of a metered spray to deliverthese formulations, in reality it would be impossible to obtain anon-occlusive delivery system with a short application time and stillmaintain a clinically useful transdermal penetration enhancement.

German patent application DE 4334553-A1 to Jenapharm GmbH discloses apharmaceutical liquid system consisting of a drug (diclofenac), alipophilic phase, a volatile component and appropriate antioxidants,preservatives or stabilisers. This system relies on supersaturation toincrease the flux rate of dermal absorption. An application chamber isused to prevent accidental precipitation of the supersaturated drugdelivery system over the application time of 150 minutes.

Japanese patent JP 61-268631 to Showa Denko KK discloses dermalpenetration enhancers suitable for use with water-soluble drugs. Thedermal penetration enhancers disclosed include 1-5 carbon fatty acidesters of para-aminobenzoic acid but their chemical structures are quitedistinct from the compounds used in the present invention, and thephysicochemical properties of the 1-5 carbon fatty acid esters ofpara-aminobenzoic acid are markedly different to those of the presentinvention. For example the octanol-water partition coefficients for allthe 1-5 carbon fatty acid esters of para-aminobenzoic acid are at least200 fold lower than those of the present invention. Also the preferreddermal penetration enhancer disclosed in JP 61-268631 is the 2 carbonfatty acid ester of para-aminobenzoic acid (or Benzocaine) which has anoctanol-water partition coefficient which is more than 8000 fold lowerthan those of the present invention. Unlike those of the presentinvention, the preferred dermal penetration enhancer disclosed in JP61-268631 has significant pharmacological properties in that it is alocal anaesthetic, which has also been reported to cause irritant andallergic skin reactions. The compounds used in the present inventionfulfil the ideal properties of a dermal penetration enhancer in thatthey are non-irritant and pharmacologically inert [Barry, B. W. VehicleEffect: What Is an Enhancer? In: Topical Drug Bioavailability,Bioequivalence, and Penetration. Shah, V. P.; Maibach, H. I. Eds. PlenumPress: New York, 1993; pp 261-276.].

It was not surprising then to find that in previous studies [Feldmann,et al., Arch. Derm., 94, 649, 1996; Coldman, et al., J. Pharm. Sci.,58(9), 119, 1969; and Bhatt, et al., Int. J. Pharm., 50, 157, 1989]where low volumes of non-occlusive volatile:non-volatile vehicles hadbeen applied to the skin, the extent of drug delivery was very limited.To date the only formulations that have been employed clinically areeither for local therapies, such as topical minoxidil and topicalnon-steroidal antiinflammatories, or for transdermal drug delivery ofcompounds which readily diffuse across the skin such as glyceryltrinitrate and isosorbide dinitrate. As the permeability coefficient ofsex hormones, for example, are an order of magnitude lower than glyceryltrinitrate, a marked penetration enhancement effect would be needed toachieve clinically acceptable transdermal drug delivery.

It is desirable to have a clinically acceptable non-occlusivetransdermal drug delivery system where the drug and penetration enhancerundergoes rapid partitioning into the skin to allow a convenientapplication time, leaving no residual formulation on the skin surface,and maintaining good substantivity within the skin. Thesecharacteristics can overcome problems such as a loss of drug penetrationor possibly a transfer of the drug from the treated individual toanother upon intimate contact, such as that observed for a testosteroneointment being used for a male patient, but which caused virilization inhis female sexual partner [Delance, et al., Lancet, 1, 276, 1984].

It is an object of the present invention to overcome or at leastalleviate one or more of the abovementioned disadvantages of the priorart systems.

According to a first aspect of the present invention there is provided atransdermal drug delivery system which comprises at least onephysiologically active agent or prodrug thereof and at least one dermalpenetration enhancer; characterised in that the dermal penetrationenhancer is a safe skin-tolerant ester sunscreen.

The present invention also provides use of a safe skin-tolerant estersunscreen as a dermal penetration enhancer.

The present inventors have found a new class of dermal penetrationenhancers being skin-tolerant ester sunscreens, which are generallyconsidered safe by the FDA (US). Compounds such as octyldimethyl-para-aminobenzoate (Padimate O) and octyl salicylate have beenextensively used over the last ten to twenty years as safe and effectivesunscreens in concentrations up to 8% v/v for Padimate O and 5% v/v foroctyl salicylate.

Dermal penetration enhancers of the present invention are preferablyesters of formula (I):

wherein R¹ is hydrogen, lower alkyl, lower alkoxy, halide, hydroxy orNR³R⁴;

R² is long chain alkyl;

R³ and R⁴ are each independently hydrogen, lower alkyl or R³ and R⁴together with the nitrogen atom to which they are attached form a 5- or6-membered heterocyclic ring;

n is 0 or 1; and

q is 1 or 2.

More preferably the ester is a long chain alkyl para-aminobenzoate, longchain alkyl dimethyl-para-aminobenzoate, long chain alkyl cinnamate,long chain alkyl methoxycinnamate or long chain alkyl salicylate; mostpreferably octyl dimethyl-para-aminobenzoate, octylpara-methoxycinnamate, octyl salicylate or isoamyl salicylate.

The drug delivery systems according to the invention may comprise anyphysiologically active agent together with the penetration enhancerincorporated into a dosage form for topical application to the skin ormucous membranes of animals. Suitable dosage forms include creams,lotions, gels, ointments, suppositories, mousses, spray, for examplenasal sprays, aerosols, buccal and sublingual tablets, gingival andbuccal patches or any one of a variety of transdermal devices for use inthe continuous administration of systematically active drugs byabsorption through the skin, oral mucosa or other membranes. Someexamples of suitable vehicles are given in U.S. Pat. Nos. 3,598,122,3,598,123, 3,742,951, 3,814,097, 3,921,636, 3,993,072, 3,993,073,3,996,934, 4,031,894, 4,060,084, 4,069,307, 4,201,211, 4,230,105,4,292,299, 4,292,303, 5,323,769, 5,023,085, 5,474,783, 4,941,880 andU.S. Pat. No. 4,077,407. These patents also disclose a variety ofspecific systematically active agents which may also be useful intransdermal delivery in adjunct to those of this invention. Thesedisclosures are thus hereby incorporated herein by reference.

Physiologically active agents that may be used in the percutaneous ortransdermal drug delivery system of the present invention include anylocally or systemically active agents which are compatible with thedermal penetration enhancers of the present invention and which can bedelivered through the skin with the assistance of the dermal penetrationenhancer to achieve a desired effect. These active agents (grouped bytherapeutic class) include:

Alimentary System

Antidiarrhoeals such as diphenoxylate, loperamide and hyoscyamine.

Cardiovascular System

Antihypertensives such as hydralazine, minoxidil, captopril, enalapril,clonidine, prazosin, debrisoquine, diazoxide, guanethidne, methyldopa,reserpine, trimetaphan.

Calcium channel blockers such as diltiazem, felodopine, amlodipine,nitrendipine, nifedipine and verapamil.

Antiarrhyrthmics such as amiodarone, flecainide, disopyramide,procainamide, mexiletene and quinidine.

Antiangina agents such as glyceryl trinitrate, erythritol tetranitrate,pentaerythritol tetranitrate, mannitol hexanitrate, perhexilene,isosorbide dinitrate and nicorandil. Beta-adrenergic blocking agentssuch as alprenolol, atenolol, bupranolol, carteolol, labetalol,metoprolol, nadolol, nadoxolol, oxprenolol, pindolol, propranolol,sotalol, timolol and timolol maleate.

Cardiotonic glycosides such as digoxin and other cardiac glycosides andtheophylline derivatives.

Adrenergic stimulants such as adrenaline, ephedrine, fenoterol,isoprenaline, orciprenaline, rimeterol, salbutamol, salmeterol,terbutaline, dobutamine, phenylephrine, phenylpropanolamine,pseudoephedrine and dopamine.

Vasodilators such as cyclandelate, isoxsuprine, papaverine,dipyrimadole, isosorbide dinitrate, phentolamine, nicotinyl alcohol,co-dergocrine, nicotinic acid, glyceryl trinitrate, pentaerythritoltetranitrate and xanthinol.

Antimigraine preparations such as ergotamine, dihydroergotamine,methysergide, pizotifen and sumatriptan.

Drugs Affecting Blood and Haemopoietic Tissues

Anticoagulants and thrombolytic agents such as warfarin, dicoumarol, lowmolecular weight heparins such as enoxaparin; streptokinase and itsactive derivatives. Haemostatic agents such as aprotinin, tranexamicacid and protamine.

Central Nervous System

Analgesics, antipyretics including the opiod analgesics-such asbuprenorphine, dextromoramide, dextropropoxyphene, fentanyl, alfentanil,sufentanil, hydromorphone, methadone, morphine, oxycodone, papaveretum,pentazocine, pethidine, phenoperidine, codeine and dihydrocodeine.Others include acetylsalicylic acid (aspirin), paracetamol, andphenazone.

Hypnotics and sedatives such as the barbiturates, amylobarbitone,butobarbitone and pentobarbitone and other hypnotics and sedatives suchas choral hydrate, chlormethiazole, hydroxyzine and meprobamate.

Antianxiety agents such as the benzodiazepines, alprazolam, bromazepam,chlordiazepoxide, clobazam, chlorazepate, diazepam, flunitrazepam,flurazepam, lorazepam, nitrazepam, oxazepam, temazepam and triazolam.

Neuroleptic and antipsychotic drugs such as the phenothiazines,chlorpromazine, fluphenazine, pericyazine, perphenazine, promazine,thiopropazate, thioridazine and trifluoperazine and the butyrophenones,droperidol and haloperidol and the other antipsychotic drugs such aspimozide, thiothixene and lithium.

Antidepressants such as the tricyclic antidepressants amitryptyline,clomipramine, desipramine, dothiepin, doxepin, imipramine,nortriptyline, opipramol, protriptyline and trimipramine and thetetracyclic antidepressants such as mianserin and the monoamine oxidaseinhibitors such as isocarboxazid, phenelizine, tranylcypromine andmoclobemide and selective serotonin re-uptake inhibitors such asfluoxetine, paroxetine, citalopram, fluvoxamine and sertraline.

CNS stimulants such as caffeine.

Anti-alzheimer's agents such as tacrine.

Antiparkinson agents such as amantadine, benserazide, carbidopa,levodopa, benztropine, biperiden, benzhexol, procyclidine and dopamine-2agonists such asS(-)-2-(N-propyl-N-2-thienylethylamino)-5-hydroxytetralin (N-0923).

Anticonvulsants such as phenytoin, valproic acid, primidone,phenobarbitone, methylphenobarbitone and carbamazepine, ethosuximide,methsuximide, phensuximide, sulthiame and clonazepam.

Antiemetics, antinauseants such as the phenothiazines, prochloperazine,thiethylperazine and 5HT-3 receptor antagonists such as ondansetron andgranisetron and others such as dimenhydrinate, diphenhydramine,metoclopramide, domperidone, hyoscine, hyoscine hydrobromide, hyoscinehydrochloride, clebopride and brompride.

Musculoskeletal System

Non-steroidal anti-inflammatory agents including their racemic mixturesor individual enantiomers where applicable, such as ibuprofen,flurbiprofen, ketoprofen, aclofenac, diclofenac, aloxiprin, aproxen,aspirin, diflunisal, fenoprofen, indomethacin, mefenamic acid, naproxen,phenylbutazone, piroxicam, salicylamide, salicylic acid, sulindac,desoxysulindac, tenoxicam, tramadol and ketoralac.

Additional non-steroidal antiinflammatory agents which can be formulatedin combination with the dermal penetration enhancers includesalicylamide, salicylic acid, flufenisal, salsalate, triethanolaminesalicylate, aminopyrine, antipyrine, oxyphenbutazone, apazone,cintazone, flufenamic acid, clonixeril, clonixin, meclofenamic acid,flunixin, colchicine, demecolcine, allopurinol, oxypurinol, benzydaminehydrochloride, dimefadane, indoxole, intrazole, mimbane hydrochloride,paranylene hydrochloride, tetrydamine, benzindopyrine hydrochloide,fluprofen, ibufenac, naproxol, fenbufen, cinchophen, diflumidone sodium,fenamole, flutiazin, metazamide, letimide hydrochloride, nexeridinehydrochloride, octazamide, molinazole, neocinchophen, nimazole,proxazole citrate, tesicam, tesimide, tolmetin, and triflumidate.

Antirheumatoid agents such as penicillamine, aurothioglucose, sodiumaurothiomalate, methotrexate and auranofin.

Muscle relaxants such as baclofen, diazepam, cyclobenzaprinehydrochloride, dantrolene, methocarbamol, orphenadrine and quinine.

Agents used in gout and hyperuricaemia such as allopurinol, colchicine,probenecid and sulphinpyrazone.

Hormones and Steroids

Oestrogens such as oestradiol, oestriol, oestrone, ethinyloestradiol,mestranol, stilboestrol, dienoestrol, epioestriol, estropipate andzeranol.

Progesterone and other progestagens such as allyloestrenol,dydrgesterone, lynoestrenol, norgestrel, norethyndrel, norethisterone,norethisterone acetate, gestodene, levonorgestrel, medroxyprogesteroneand megestrol.

Antiandrogens such as cyproterone acetate and danazol.

Antioestrogens such as tamoxifen and epitiostanol and the aromataseinhibitors, exemestane and 4-hydroxy-androstenedione and itsderivatives.

Androgens and anabolic agents such as testosterone, methyltestosterone,clostebol acetate, drostanolone, furazabol, nandrolone oxandrolone,stanozolol, trenbolone acetate, dihydro-testosterone,17-α-methyl-19-nortestosterone and fluoxymesterone.

5-alpha reductase inhibitors such as finasteride, turosteride, LY-191704and MK-306.

Corticosteroids such as betamethasone, betamethasone valerate,cortisone, dexam{overscore (e)}thasone, dexamethasone 21-phosphate,fludrocortisone, flumethasone, fluocinonide, fluocinonide desonide,fluocinolone, fluocinolone acetonide, fluocortolone, halcinonide,halopredone, hydrocortisone, hydrocortisone 17-valerate, hydrocortisone17-butyrate, hydrocortisone 21-acetate methylprednisolone, prednisolone,prednisolone 21-phosphate, prednisone, triamcinolone, triamcinoloneacetonide.

Further examples of steroidal antiinflammatory agents for use in theinstant compositions include include cortodoxone, fluoracetonide,fludrocortisone, difluorsone diacetate, flurandrenolone acetonide,medrysone, amcinafel, amcinafide, betamethasone and its other esters,chloroprednisone, clorcortelone, descinolone, desonide, dichlorisone,difluprednate, flucloronide,flumethasone, flunisolide, flucortolone,fluoromethalone, fluperolone, fluprednisolone, meprednisone,methylmeprednisolone, paramethasone, cortisone acetate, hydrocortisonecyclopentylpropionate, cortodoxone, flucetonide, fludrocortisoneacetate, flurandrenolone acetonide, medrysone, amcinafal, amcinafide,betamethasone, betamethasone benzoate, chloroprednisone acetate,clocortolone acetate, descinolone acetonide, desoximetasone,dichlorisone acetate, difluprednate, flucloronide, flumethasonepivalate, flunisolide acetate, fluperolone acetate, fluprednisolonevalerate, paramethasone acetate, prednisolamate, prednival,triamcinolone hexacetonide, cortivazol, formocortal and nivazol.

Pituitary hormones and their active derivatives or analogs such ascorticotrophin, thyrotropin, follicle stimulating hormone (FSH),luteinising hormone (LH) and gonadotrophin releasing hormone (GnRH).

Hypoglycaemic agents such as insulin, chlorpropamide, glibenclamide,gliclazide, glipizide, tolazamide, tolbutamide and metformin.

Thyroid hormones such as calcitonin, thyroxine and liothyronine andantithyroid agents such as carbimazole and propylthiouracil.

Other miscelaneous hormone agents such as octreotide.

Pituitary inhibitors such as bromocriptine.

Ovulation inducers such as clomiphene.

Genitourinary System

Diuretics such as the thiazides, related diuretics and loop diuretics,bendrofluazide, chlorothiazide, chlorthalidone, dopamine,cyclopenthiazide, hydrochlorothiazide, indapamide, mefruside,methycholthiazide, metolazone, quinethazone, bumetanide, ethacrynic acidand frusemide and pottasium sparing diuretics, spironolactone, amilorideand triamterene.

Antidiuretics such as desmopressin, lypressin and vasopressin includingtheir active derivatives or analogs.

Obstetric drugs including agents acting on the uterus such asergometrine, oxytocin and gemeprost.

Prostaglandins such as alprostadil (PGE1), prostacyclin (PGI2),dinoprost (prostaglandin F2-alpha) and misoprostol.

Antimicrobials

Antimicrobials including the cephalosporins such as cephalexin,cefoxytin and cephalothin.

Penicillins such as amoxycillin, amoxycillin with clavulanic acid,ampicillin, bacampicillin, benzathine penicillin, benzylpenicillin,carbenicillin, cloxacillin, methicillin, phenethicillin,phenoxymethylpenicillin, flucloxacillin, mezlocillin, piperacillin,ticarcillin and azlocillin.

Tetracyclines such as minocycline, chlortetracycline, tetracycline,demeclocycline, doxycycline, methacycline and oxytetracycline and othertetracycline-type antibiotics. Aminoglycosides such as amikacin,gentamicin, kanamycin, neomycin, netilmicin and tobramycin.

Antifungais such as amorolfine, isoconazole, clotrimazole, econazole,miconazole, nystatin, terbinafine, bifonazole, amphotericin,griseofulvin, ketoconazole, fluconazole and flucytosine, salicylic acid,fezatione, ticlatone, tolnaftate, triacetin, zinc, pyrithione and sodiumpyrithione.

Quinolones such as nalidixic acid, cinoxacin, ciprofloxacin, enoxacinand norfloxacin. Sulphonamides such as phthalylsulphthiazole,sulfadoxine, sulphadiazine, sulphamethizole and sulphamethoxazole.

Sulphones such as dapsone.

Other miscellaneous antibiotics such as chloramphenicol, clindamycin,erythromycin, erythromycin ethyl carbonate, erythromycin estolate,erythromycin glucepate, erythromycin ethylsuccinate, erythromycinlactobionate, roxithromycin, lincomycin, natamycin, nitrofurantoin,spectinomycin, vancomycin, aztreonam, colistin IV, metronidazole,tinidazole, fusidic acid and trimethoprim; 2-thiopyridine N-oxide;halogen compounds, particularly iodine and iodine compounds such asiodine-PVP complex and diiodohydroxyquin; hexachlorophene;chlorhexidine; chloroamine compounds; benzoylperoxide;.

Antituberculosis drugs such as ethambutol, isoniazid, pyrazinamide,rifampicin and clofazimine.

Antimalarials such as primaquine, pyrimethamine, chloroquine,hydroxychloroquine, quinine, mefloquine and halofantrine.

Antiviral agents such as acyclovir and acyclovir prodrugs, famciclovir,zidovudine, didanosine, stavudine, lamivudine, zalcitabine, saquinavir,indinavir, ritonavir, n-docosanol, tromantadine and idoxuridine.

Anthelmintics such as mebendazole, thiabendazole, niclosamide,praziquantel, pyrantel embonate and diethylcarbamazine.

Cytotoxic agents such as plicamycin, cyclophosphamide, dacarbazine,fluorouracil and its prodrugs [described,for example, in InternationalJournal of Pharmaceutics 111, 223-233 (1994)], methotrexate,procarbazine, 6-mercaptopurine and mucophenolic acid.

Metabolism

Anorectic and weight reducing agents including dexfenfluramine,fenfluramine, diethylpropion, mazindol and phentermine.

Agents used in hypercalcaemia such as calcitriol, dihydrotachysterol andtheir active derivatives or analogs.

Respiratory System

Antitussives such as ethylmorphine, dextromethorphan and pholcodine.

Expectorants such as acetylcysteine, bromhexine, emetine, guaiphenesin,ipecacuanha ans saponins.

Decongestants such as phenylephrine, phenylpropanolamine anspseudoephedrine.

Bronchospasm relaxants such as ephedrine, fenoterol, orciprenaline,rimiterol, salbutamol, sodium cromoglycate, cromoglycic acid and itsprodrugs [described,for example, in International Journal ofPharmaceutics 7, 63-75 (1980)], terbutaline, ipratropium bromide,salmeterol and theophylline and theophylline derivatives.

Allergy and Immune System

Antihistamines such as meclozine, cyclizine, chlorcyclizine,hydroxyzine, brompheniramine, chlorpheniramine, clemastine,cyproheptadine, dexchlorpheniramine, diphenhydramine, diphenylamine,doxylamine, mebhydrolin, pheniramine, tripolidine, azatadine,diphenylpyraline, methdilazine, terfenadine, astemizole, loratidine andcetirizine.

Local anaesthetics such as bupivacaine, amethocaine, lignocaine,cinchocaine, dibucaine, mepivacaine, prilocaine and etidocaine.

Stratum corneum lipids, such as ceramides, cholesterol and free fattyacids, for improved skin barrier repair [Man, et al. J. Invest.Dermatol., 106(5), 1096, 1996].

Neuromuscular blocking agents such as suxamethonium, alcuronium,pancuronium, atracurium, gallamine, tubocurarine and vecuronium.

Smoking cessation agents such as nicotine, bupropion and ibogaine.

Insecticides and other pesticides which are suitable for local orsystemic application.

Dermatological agents, such as vitamins A and E, vitamin E acetate andvitamin E sorbate.

Allergens for desensitisation such as house dust mite allergen.

Nutritional agents, such as vitamins, essential amino acids andessential fats.

Keratolytics such as the alpha-hydroxy acids, glycollic acid andsalicylic acid.

Psychicenergisers, such as 3-(2-aminopropyl)indole,3-(2-aminobutyl)indole, and the like.

Anti-acne agents such as containing isotretinoin, tretinoin and benzoylperoxide.

Anti-psoriasis agents such as containing etretinate, cyclosporin andcalcipotriol.

Anti-itch agents such as capsaicin and its derivatives such asnonivamide [Tsai, et al. Drug. Dev. Ind. Pharm., 20(4), 719, 1994].

Anticholinergic agents, which are effective for the inhibition ofaxillary sweating and for the control of prickly heat. Theantiperspirrant activity of agents such as methatropine nitrate,propantheline bromide, scopolamine, methscopolamine bromide, and the newclass of soft antiperspirants, quaternary acyloxymethyl ammnonium salts[described, for example, by Bodor et al, J. Med. chem. 23, 474 (1980)and also in United Kingdom Specification No. 2010270, published 27 Jun.1979].

Other physiologically active peptides and proteins, small tomedium-sized peptides, e.g., vasopressin and human growth hormone.

Whilst it is preferred that the active agent and penetration enhancer bedelivered by simultaneous administration, the penetration enhancer maybe applied before or after the application of the physiologically activeagent, if desired.

The present invention also provides a transdermal drug delivery systemwhich comprises at least one physiologically active agent or prodrugthereof, at least one dermal penetration enhancer and at least onevolatile liquid; characterised in that the dermal penetration enhanceris a safe skin-tolerant ester sunscreen.

According to a second aspect of the present invention there is provideda non-occlusive, percutaneous or transdermal drug delivery system whichcomprises:

(i) an effective amount of at least one physiologically active agent orprodrug thereof;

(ii) at least one non-volatile dermal penetration enhancer; and

(iii) at least one volatile liquid;

characterised in that

the dermal penetration enhancer is adapted to transport thephysiologically active agent across a dermal surface or mucosal membraneof an animal, including a human, when the volatile liquid evaporates, toform a reservoir or depot of a mixture comprising the penetrationenhancer and the physiologically active agent or prodrug within saidsurface or membrane; and

the dermal penetration enhancer is of low toxicity to, and is toleratedby, the dermal surface or mucosal membrane of the animal.

The present invention also provides a method for administering at leastone systemic or locally acting physiologically active agent or prodrugthereof to a animal which comprises applying an effective amount of thephysiologically active agent in the form of a drug delivery systemaccording to the present invention.

Furthermore, the present invention provides a method for the treatmentor prophylaxis of a disease or condition in a animal which comprisesadministering to a dermal surface or mucosal membrane of said animal inneed of such treatment a therapeutically effective amount of a drugdelivery system according to the present invention.

The invention further provides apparatus for the controlled applicationof an aerosol or spray composition to the dermal surface or mucosalmembrane of an animal, which comprises a shroud as describedhereinafter.

Preferably the animal is a human but the invention also extends to thetreatment of non-human animals.

Preferably the non-occlusive drug delivery system is not supersaturatedwith respect to the physiologically active agent or prodrug. As thevolatile liquid of the non-occlusive drug delivery system evaporates,the resulting non-volatile composition is rapidly driven into the dermalsurface or mucosal membrane. It is possible that as the volatile liquidevaporates, the non-volatile dermal penetration enhancer becomessupersaturated with respect to the active agent. However, it ispreferred that any supersaturation does not occur before transport ofthe resulting non-volatile composition across the epidermal surface hasoccurred.

It is most desirable that, after application of the non-occlusive,percutaneous or transdermal drug delivery system, the volatile componentof the delivery system evaporates and the area of skin to which the drugdelivery system was applied becomes touch-dry. Preferably said area ofskin becomes touch-dry within 10 minutes, more preferably within 3minutes, most preferably within 1 minute.

The group of dermal penetration enhancing ester sunscreen compounds ofthe present invention are particularly suitable for non-occlusivetransdermal delivery of active agents through the skin and membranes ofa animal. These dermal penetration enhancing compounds are of lowtoxicity to the skin and are excellent promoters of percutaneous andoral mucosal (especially gingival) absorption. In audition to the dermalpenetration enhancers of the present invention, known dermal penetrationenhancers may be employed in the non-occlusive transdermal drug deliverysystem of the present invention. These known dermal penetrationenhancers include laurocapram (Azone®) and laurocapram derivatives, suchas those 1-alkylazacycloheptan-2-ones specified in U.S. Pat. No.5,196,410, and oleic acid and its ester derivatives, such as methyl,ethyl, propyl, isopropyl, butyl, vinyl and glycerylmonooleate, andsorbitan esters such as sorbitan monolaurate and sorbitan monooleate,and other fatty acid esters such as isopropyl laurate, isopropylmyristate, isopropyl palmitate, diisopropyl adipate, propylene glycolmonolaurate and propylene glycol monooleate, and long chain alkyl estersof 2-pyrrolidone, particularly the 1-lauryl, 1-hexyl and1-(2-ethylhexyl) esters of 2-pyrollidene and those dermal penetrationenhancers given in U.S. Pat. No. 5,082,866, particulary dodecyl(N,N-dimethylamino) acetate and dodecyl (N,N-dimethylamino) propionateand in U.S. Pat. No. 4,861,764, particularly 2-n-nonyl-1-3-dioxolane.

Preferred known dermal penetration enhancers are laurocapram andlaurocapram derivatives, such as those 1 -alkylazacycloheptan-2-onesspecified in U.S. Pat. No. 5,196,410, and oleic acid and its esterderivatives, such as methyl, ethyl, propyl, isopropyl, butyl, vinyl andglycerylmonooleate, and those given in U.S. Pat. No. 5,082,866,particularly dodecyl (N,N-dimethylamino) acetate and dodecyl(N,N-dimethylamino) propionate and in U.S. Pat. No. 4,861,764,particularly 2-n-nonyl-1-3-dioxolane. Most preferred known dermalpenetration enhancers are oleic acid and its ester derivatives, such asmethyl, ethyl, propyl, isopropyl, butyl, vinyl and glycerylmonooleate,and those given in U.S. Pat. No. 5,082,866, particulary dodecyl(N,N-dimethylamino) acetate and dodecyl (N,N-dimethylamino) propionateand in U.S. Pat. No. 4,861,764, particularly 2-n-nonyl-1-3-dioxolane.

Preferred volatile liquids of the present invention include safeskin-tolerant solvents such as ethanol and isopropanol. An aerosolpropellant, such as dimethyl ether, may constitute a volatile liquid forthe purpose of the present invention.

Surprisingly the group of dermal penetration compounds identifiedenhance the absorption of active agents and prodrugs thereof through theskin and mucous membranes while avoiding the significant pharmacologicaldisadvantages and toxicities of prior art enhancers. Additionally, thegroup of compounds of the invention surprisingly exhibit appreciablepenetration into and substantivity for the outer layers of the skin,namely the stratum corneum which has previously presented a formidablebarrier to percutaneous drug absorption.

In drug delivery systems according to the first aspect of the presentinvention a pharmaceutical compounding agent, co-solvent, surfactant,emulsifier, antioxidant, preservative, stabiliser, diluent or a mixtureof two or more of said components may be incorporated in these systemsas is appropriate to the particular route of administration and dosageform. The amount and type of components used should be compatible withthe dermal penetration enhancers of this invention as well as with theactive ingredient. A co-solvent or other standard adjuvant, such as asurfactant, may be required to maintain the agent in solution orsuspension at the desired concentration.

The pharmaceutical compounding agents can include paraffin oils, esterssuch as isopropyl myristate, ethanol, silicone oils and vegetable oils.These are preferably used in the range 1 to 50%. Surfactants such asethoxylated fatty alcohols, glycerol mono stearate, phosphate esters,and other commonly used emulsifiers and surfactants preferably in therange of 0.1 to 10% may be used, as may be preservatives such ashydroxybenzoate esters for preservation of the compound preferably inamounts of 0.01% to 0.5%. Typical co-solvents and adjuvants may be ethylalcohol, isopropyl alcohol, acetone, dimethyl ether and glycol etherssuch as diethylene glycol mono ethyl ether. These may be used in amountsof 1 to 50%.

In drug delivery systems according to the second aspect of the presentinvention, whilst a pharmaceutical compounding agent, co-solvent,surfactant, emulsifier, antioxidant, preservative, stabiliser, diluentor a mixture of two or more of said components may be incorporated,these must be compatible with the ability of the system to becometouch-dry after application.

Because of the effect of the penetration enhancer of the invention, thedosage of the physiologically active agent may often be less than thatconventionally used. It is proposed that, a dosage near the lower end ofthe useful range of the particular agent may be employed initially andincreased as indicated from the observed response if necessary.

The concentration of physiologically active agent used in the drugdelivery system will depend on its properties and may be equivalent tothat-normally utilised for the particular agent in conventionalformulations. Both the amount of physiologically active agent and theamount of penetration enhancer will be influenced by the type of effectdesired. For example, if a more localised effect is required in treatinga superficial infection with an antibacterial agent, lower amounts ofphysiologically active agents and lower concentrations of enhancer maybe appropriate. Where deeper penetration is desired, as in the case oflocal anaesthesia, a higher concentration of enhancer may beappropriate.

Where it is desired to achieve systemic concentration of an agent,proportionately higher concentrations of the enhancer of the inventionmay be required in the transdermal drug delivery system of the presentinvention, and the amount of active substance included in thecomposition should be sufficient to provide the blood level desired.

The concentration of absorption/penetration enhancer may be in the rangefrom 10-10,000 weight percent of absorption/penetration enhancer basedupon the weight of active ingredient. The ratio of penetration enhancerto active ingredient may vary considerably and will be governed as muchas anything, by the pharmacological results that are required to beachieved. In principle, it is desirable that as little absorptionenhancer as possible is used. On the other hand, for some actives, itmay well be that the upper range of 10,000% by weight will be required.It is preferred that the penetration enhancer and active are inapproximately equal proportions.

Surprisingly, it has been found that a large range of systemic drugs canbe delivered to a subject in need thereof by the non-occlusive drugdelivery system and methods of the present invention. That is, the drugdelivery system delivers the physiologically active agent to a animalwithout the need for an occlusive patch device. The efficacy of knownsystemic drug delivery systems, and in particular transdermal patchdevices is maintained, and in some cases is increased by use ofnon-occlusive, percutaneous or transdermal drug delivery systems of thepresent invention.

A particular advantage of the non-occlusive drug delivery system of thepresent invention is that patient compliance is improved as the systemdoes not occlude the skin or membrane and therefore local irritation andallergic sensitisation problems arising from prolonged exposure of theskin to both the delivery system of occlusive transdermal patch devicesand the adhesive used to affix these patches to the skin are reduced.

The following definitions apply through this description and the claimswhich follow.

The term “mucous membrane” refers generally to any of the mucousmembranes in the body, absorption through the mucous membranes of theoral cavity which is of particular interest. Thus, buccal, sublingual,gingival and palatal absorption are specifically contemplated by thepresent invention. In a preferred embodiment, the penetration enhancersof the present invention are used to improve absorption through thoseoral tissues which most resemble the skin in their cellular structure,i.e. the gingiva and palate.

The term “physiologically active agent” is used herein to refer to abroad class of useful chemical and therapeutic agents.

The term “physiologically active” in describing the agents contemplatedherein is used in a broad sense to comprehend not only agents having adirect pharmacological effect on the host, but also those having anindirect or observable effect which is useful in the medical arts.

A “prodrug” of a physiologically active agent herein means astructurally related compound or derivative of an active compound whichin the animal body is converted to the desired physiologically activecompound. The prodrug itself may have little or none of the desiredactivity.

The terms “percutaneous” and “transdermal” are used herein in thebroadest sense to refer to being able to pass through unbroken skin.

The term “dermal penetration enhancer” is used herein in its broadestsense to refer to an agent which improves the rate of percutaneoustransport of active agents across the skin for use and delivery ofactive agents to organisms such as animals, whether it be for localapplication or systemic delivery.

The term “non-occlusive” is used herein in its broadest sense to referto not trapping or closing the skin to the atmosphere by means of apatch device, fixed reservoir, application chamber, tape, bandage,sticking plaster, or the like which remains on the skin at the site ofapplication for a prolonged length of time.

The term “stratum corneum” is used herein in its broadest sense to referto the outer layer of the skin, which is comprised of (approximately 15)layers of terminally differentiated keratinocytes made primarily of theproteinaceous material keratin arranged in a ‘brick and mortar’ fashionwith the mortar being comprised of a lipid matrix made primarily fromcholesterol, ceramides and long chain fatty acids. The stratum corneumcreates the rate-limiting barrier for diffusion of the active agentacross the skin.

The term “skin-depot” is used herein in its broadest sense to refer to areservoir or deposit of active agent and dermal penetration enhancerwithin the stratum corneum, whether it be intra-cellular (withinkeratinocytes) or inter-cellular.

The term “volatile:non-volatile liquid vehicle” is used in the art torefer to a liquid pharmaceutical vehicle comprising a volatile liquidmixed with a non-volatile liquid vehicle, such as a dermal penetrationenhancer. A system or vehicle comprising a volatile liquid mixed with anon-volatile dermal penetration enhancer when described herein is usedin its broadest sense to include those systems known asvolatile:non-volatile liquid vehicles.

Alkyl and alkoxy groups referred to herein may be either straight chainor branched. The term “lower alkyl” means alkyl groups containing from 1to 5 carbon atoms. The term “lower alkoxy has a similar meaning. Theterm “long chain alkyl” means alkyl groups containing from 5 to 18carbon atoms, more preferably 6 to 18 carbon atoms. The term “halide”means fluoride, chloride, bromide or iodide. The term “heterocyclicring” is herein defined to mean a ring of carbon atoms containing atleast one hetero atom, and further the ring may be saturated orunsaturated to any allowable degree.

The term “sunscreen” is used herein in its broadest sense to refer to achemical agent capable of filtering out ultraviolet light.

The non-occlusive, percutaneous or transdermal drug delivery system ofthe present invention enables a wide range of physiologically activeagents to be delivered through the skin to achieve a desired systemiceffect. The drug delivery system preferably comprises the active agentintimately mixed with a non-volatile dermal penetration enhancer and avolatile liquid. Where the drug delivery system is applied to the skin,the active agent and non-volatile liquid are thermodynamically driveninto the skin as the volatile liquid evaporates. Once within the skinthe non-volatile liquid may either disrupt the lipid matrix and/or actas a solubilizer to allow an enhanced penetration rate of the activeagent through the skin and into the subject being treated. In this way,the dermal penetration enhancer acts as a vehicle and many systemicactive agents are able to be transdermally administered to an animal.

It is believed that the non-volatile dermal penetration enhancer isreadily absorbed into the stratum corneum in sufficient quantities toform a reservoir or depot of the dermal penetration enhancer within thestratum corneum. The dermal penetration enhancer also contains theactive agent to be administered and as the dermal penetration enhancercrosses through the skin to form the skin-depot, the active agentcontained therein is transported through the skin and contained withinthe depot. These depots are believed to form within the lipid matrix ofthe stratum corneum wherein the lipid matrix creates a rate-limitingbarrier for diffusion of the active agent across the skin and allows thedermally administered active agent to be systemically released over aperiod of time, usually up to 24 hours.

Once the volatile liquid of the non-occlusive drug delivery system hasevaporated, driving the mixture of non-volatile dermal penetrationenhancer and active agent into the stratum corneum, the outer surface ofthe skin is then substantially free of active agent and non-volatiledermal penetration enhancer. Normal touching, wearing of clothes,rinsing or even washing of the skin will not, to any significant extent,affect delivery of the drug or displace either the active agent or thenon-volatile dermal penetration enhancer, once the volatile liquid hasevaporated.

This is in contrast to prior-art systems where supersaturated solutionsare used to increase the rate of drug permeation across the skin. Suchsupersaturated solutions are susceptible to ready precipitation andrequire stabilization, such as with polymers, or protection fromexternal surfaces or objects which may effect nucleation.

The rate of absorption of the physiologically active agent via thestratum corneum is increased by the non-volatile dermal penetrationenhancer. The active agent may be dissolved or suspended in the dermalpenetration enhancer at the time when it is being transported from thesurface of the skin and into the stratum corneum. The performance of thedermal penetration enhancer to deliver a desired active agent varieswith differences in both the nature of the dermal penetration enhancerand active agent. It is understood that different dermal penetrationenhancers may need to be selected to be appropriate for delivery ofvarious active agents.

Physiologically active agents that may be used in the percutaneous ortransdermal drug delivery system of the present invention include anylocally or systemically active agents which are compatible with thenon-volatile dermal penetration enhancers and volatile liquids of thepresent invention and which can be delivered through the skin with theassistance of the dermal penetration enhancer to achieve a desiredeffect.

Preferred active agents include steroids and other hormone derivatives,more preferably testosterone, oestradiol, ethinyloestradiol,progesterone, norethisterone acetate and gestodene; and non-steroidalanti-inflammatory drugs, preferably ibuprofen, ketoprofen, flurbiprofen,naproxen and diclofenac; and opioid analgesics, preferably fentanyl andbuprenorphine; and antinauseants, preferably prochlorperazine,metochlopramide, ondansetron and scopolamine; and antioestrogens,preferably tamoxifen and epitiostanol and the aromatase inhibitors,preferably exemestane and 4-hydroxy-androstenedione and its derivatives;and 5-alpha reductase inhibitors, preferably finasteride, turosteride,LY191704 and MK-306; and anxiolytics, preferably alprazolam; andprostaglandins, preferably alprostadil and prostacylcin and theirderivatives; and melatonin; and anti-virals, preferably n-docosanol,tromantadine and lipophilic pro-drugs of acyclovir; and low molecularweight heparin, preferably enoxaparin; and anti-migraine compounds,preferably sumatriptan; and antihypertensives, preferably clonidine,amlodipine and nitrendipine; and anti-malarials, preferably primaquine;and minoxidil and minoxidil pro-drugs; and pilocarpine; andbronchodilators, preferably salbutamol, terbutaline, salmeterol; andanti-depressants, preferably ibogaine, bupropion and rolipram; andanti-alzheimer's agents, preferably fluphenazine and haloperidol; andanti-parkinson agents, preferably N-0923; and antiandrogens, preferablycyproterone acetate; and anorectic agents, preferably mazindol.

Diseases or conditions that may be treated by using the drug deliverysystem and methods of the present invention include, but are not limitedto, male hormone replacement in testosterone deficient hypogonadal men,female hormone replacement therapy for postmenopausal women, androgenreplacement therapy for females lacking libido, male contraception,female contraception, soft tissue injury, narcotic withdrawal, severepost-operative pain, motion sickness, oestrogen dependent breast cancer,prostatic enlargement and/or prostatic cancer, alopecia and acne,anxiety disorders, male impotence, Raynauds syndrome and varicose veins,sleep disorders such as jetlag, herpes virus infections, deep veinthrombosis, migraine, high blood pressure, malaria, diagnosis of cysticfibrosis and asthma, particularly nocturnal asthma, smoking cessation,psychotic disorders, severe postnatal depression, virilisation andobesity.

The foregoing lists are by no means intended to be exhaustive and anyphysiologically active agent that is compatible with the preferredvolatile liquids and non-volatile dermal penetration enhancers of thedrug delivery system may be applied by the method of the presentinvention to treat any appropriate disease or condition.

The drug delivery system of the present invention may be applied to theskin by means of an aerosol, spray, pump-pack, brush, swab, or otherapplicator. Preferably, the applicator provides either a fixed orvariable metered dose application such as a metered dose aerosol, astored-energy metered dose pump or a manual metered dose pump. Theapplication is most preferably performed by means of a topical metereddose aerosol combined with an actuator nozzle shroud which togetheraccurately control the amount and/or uniformity of the dose applied. Onefunction of the shroud is to keep the nozzle at a pre-determined heightabove, and perpendicular to, the skin or membrane to which the drugdelivery system is being applied. This function may also be achieved bymeans of a spacer-bar or the like. Another function of the shroud is toenclose the area above the skin or membrane in order to prevent or limitbounce-back and/or loss of the drug delivery system to the surroundingenvironment. Preferably the area of application defined by the shroud issubstantially circular in shape.

The drug delivery system may be propelled by either pump pack or morepreferably by the use of propellants such as hydrocarbons, hydrofluorocarbons, nitrogen, nitrous oxide, carbon dioxide or ethers,preferably dimethyl ether. The non-occlusive, drug delivery system ispreferably in a single phase system as this allows less complicatedmanufacture and ease of dose uniformity. It may also be necessary toapply a number of dosages on untreated skin to obtain the desiredresult.

The invention will now be described with reference to the followingexamples and accompanying drawings. The examples and drawings are not tobe construed as limiting the invention in any way. They are included tofurther illustrate the present invention and advantages thereof.

In the drawings:

FIG. 1 is a diagrammatic representation showing the halves of astainless steel flow-through diffusion cell.

FIG. 2 is a graphical representation showing the effect of pretreatmentwith various enhancers on the diffusion of ketoprofen across shed snakeskin.

FIG. 3 is a graphical representation showing the effect of variousenhancers on the diffusion of ketoprofen across shed snake skin.

FIG. 4 is a graphical representation showing the diffusion of ibuprofenfrom gel formulations across shed snake skin.

FIG. 5 is a graphical representation showing the plasma profile oftestosterone in domestic weanling pigs after a single application of ametered dose topical aerosol. Error bars represent standard error of themean.

FIG. 6 is a graphical representation showing the plasma profile ofestradiol in domestic weanling pigs after a single application of ametered dose topical aerosol. Error bars represent standard error of themean.

FIG. 7 is a graphical representation showing the plasma profile oftestosterone in castrated domestic weanling pigs after the sixth oncedaily application of a metered dose topical aerosol. Each pointrepresents the mean of 4 individual values and the error bars representstandard error of the mean. Testosterone levels shown are baselinesubtracted and the mean baseline (±sem) on Day 1 at 0 h was 0.8ng.ml⁻¹±0.3 ng.ml⁻¹.

FIG. 8 is a graphical representation showing the predicted testosteroneinput across human skin in vivo and children's python snake skin invitro. Error bars represent standard error of the mean.

FIG. 9 is a graphical representation showing the predicted testosteroneplasma concentration in hypogonadal males after once daily dosing tosteady-state with a metered dose topical spray.

In the examples, the effectiveness of the penetration enhancers areillustrated by measuring the skin penetration of formulations of anumber of representative physiologically active agents with the dermalpenetration enhancers. Also, the skin penetration of physiologicallyactive agents was measured with other prior art penetration enhancers aswell as formulations of the physiologically active agents with commonadjuvants, which serve as control formulations. The comparisons madegenerally consisted of measuring the relative penetration through shedsnake skin of the various formulations. In every case, thoseformulations which contained the dermal penetration enhancers deliveredmore of the active agent through the skin than did the correspondingcontrol formulation or commercial preparation.

In Vitro Skin Diffusion Measurements

Shed Snake Skin

The Children's python shed snake skin was obtained during naturalshedding and the dorsal skin was used. Shed snake skin has shown to be asuitable model membrane for human skin by Itoh, et al., Use of ShedSnake Skin as a Model Membrane for In Vitro Percutaneous PenetrationStudies: Comparison with Human Skin, Pharm. Res., 7(10), 1042-1047,1990; and Rigg, et al., Shed Snake Skin and Hairless Mouse Skin as ModelMembranes for Human Skin During Permeation Studies, J. Invest.Dermatol., 94; 235-240, 1990.

Full Thickness Skin

The animals used in these investigations were obtained from the animalhouse at the Victorian College of Pharmacy, Monash University,Parkville, Australia.

a. Hairless Mouse Skin

Hairless mice of 4-8 weeks of age were used. The mouse skin was excisedand full-thickness skin was isolated from the torso, the subcutaneousfat and connective tissue removed and the skin cut into circles of 2·0cm², then placed into the diffusion cells for flux measurements.

b. Guinea Pig Skin

Adult guinea pigs of either sex (weight range 500 g-750 g) were used.The hair on the back flank and back was removed with the aid ofdepilatory wax (Arielle™) under halothane anaesthesia. Seven days later,after the stratum corneum had completely regenerated, the guinea pigswere killed and the skin removed and placed on a chilled slab. Thesubcutaneous fat and connective tissue removed and the skin cut intocircles and then placed into the diffusion cells for flux measurements.For in vivo experiments the guinea pigs were housed in individual cagesand the topical hydroquinone formulations were applied to the hair-freeareas. Each guinea pig received the test or control formulation on thecorresponding contralateral site, thus allowing each animal to act asits own control.

In Vitro Skin Diffusion Experiments in Franz-type Cells

The work using Hydroquinone was performed using vertical Franz diffusioncells which had an effective diffusional area of 1.3 cm², a receiverchamber temperature of 37 or 32 degrees Celsius and receiver chambervolume of 13 mL of normal saline.

In Vitro Skin Diffusion Experiments in Horizontal Diffusion Cells

A modified stainless steel flow-through diffusion cell assembly based onthat first shown by Cooper in J.Pharm.Sci. 73(8), 1984, was used toperform the experiments on diffusion of the drugs from various donorcompositions through the skin (either snake or hairless mouse). Theflow-through diffusion cell used to perform the present experiments isshown in FIG. 1. The cell consists of an upper section (1) and a lowersection (2). A stainless steel wire mesh support (4) is housed in arecess (5) in the lower section of the cell. The skin sample (3), cutinto a circle, is gently placed over the support (4) and the twosections (1,2) of the cells are secured together by screws (not shown),using the locating holes (9), to form a tight seal. An aperture (8) inthe upper section of the cell, which has an area of 0.79 cm² (0.5 cm indiameter) forms a well above the skin into which the topical formulationis applied. In most cases 400 microL of formulation, solution orsuspension containing the drug substance to be tested was applied evenlyover the skin. The bottom section of the cell is provided with inlet (6)and outlet (7) tubes which connect to the bottom of the recess (5) andthrough which a receptor solution was pumped by a microcassetteperistaltic pump (Watson Marlow, UK) (not shown) at a constant flow rateto maintain sink conditions. The receptor solution consisted of 50%propylene glycol in water, made isotonic with 0·9% sodium chloride andpreserved with 0·1% sodium azide or 0.1% sodium fluoride. To prevent airbubbles forming under the skin, the wire mesh (4) ensures turbulentreceptor flow. The recess (5) is filled with receptor solution prior toplacing the skin in the cell. The receptor solution was degassed byspraying the solution into fine droplets under vacuum while stirring at40° C. Degassing was repeated three times. These precautions eliminatedthe need for a bubble chamber in the diffusion cell. The diffusion cellswere set on a hollow metal heater bar which maintained normal skintemperature of 32° C. (±0.5° C.) means of heated, circulating water(Thermomix, Braun, Germany). Each diffusion cell had its receptorsolution collected via tube (7) into polyethylene vials (6 ml liquidscintillation vials, Packard instruments, Netherlands) at two or fourhour intervals for 24 hours, by means of an automated rotating fractioncollector (Retriever II, ISCO, Australia). The amount of drug in eachvial containing receptor solution was determined by reverse phase HPLC.Prior to analysis each vial was weighed with an analytical balance(Mettler AT261, Australia) and the volume calculated from the density ofthe receptor solution which was 1·0554 g/cm³ at 22° C.

The concentration of applied drug in each diffusion cell sample wasmeasured using high pressure liquid chromatography (HPLC). The receptorsolution was assayed neat, with 20 microL injected (WISP 712autoinjector, Waters, Australia) into a freshly prepared and degassed(by filtering) mobile phase. Each drug was separated using a pre columnfitted with a C18 insert and a μBandapak C18 (30 cm×3.9 nm) HPLC column(Waters). Absorbance was measured at the appropriate wavelength using aWaters tuneable absorbance detector and peak area was plotted andintegrated using a Shimadzu C-R3A chromatopac integrator. The resultsreported for each experiment are the average values of four replicatediffusion cells unless stated otherwise. The assay conditions used foreach different drug are given in each example.

EXAMPLE 1

The in vitro diffusion cell method described above was used to comparethe penetration of 400 microL of 2% w/v ketoprofen in 70% v/v aqueousethanol applied to the shed snake skin following the application of 400microL of the different dermal penetration enhancers in a 2% v/vsolution in 70% ethanol, 2 hours prior to the application of theketoprofen. The control experiment involved application of 400 microL of70% aqueous ethanol alone for 2 hours, followed by application of 400microL of the 2% ketoprofen solution. Samples were assayed according tothe method described previously. The detection wavelength was 255 nm andthe mobile phase consisted of acetonitrile:water (55:45) made to pH 3·0with orthophosphoric acid (BDH, Australia). Table 1 shows the mean fluxof ketoprofen across the snake skin over 24 hours as determined by thelinear regression of the cumulative amount of ketoprofen crossing theskin versus time (Units=microg/cm².h). FIG. 2 shows the representativemean cumulative amount versus time plots for ketoprofen.

TABLE 1 Mean flux +/− std p value relative error to Enhancement Enhancertype (microg/cm².h) control ratio Control - no 0.96 ± 0.18 — — enhancer,n = 9 Azone, n = 2 2.58 ± 0.23 0.0029 2.7 Octyl dimethyl 2.25 ± 0.140.0068 2.3 PABA, n = 3 Octylmethoxy 3.22 ± 0.28 0.0003 3.35 cinnamate, n= 3 Octyl salicylate, 27.66 ± 5.26 <0.0070 28.81 n = 2 NB. Enhancementratio = mean flux enhancer/mean flux control

Statistical significance was determined by means of a Student's t-test.Azone was selected as the standard penetration enhancer for comparisonsince it has been widely used in previous percutaneous penetrationexperiments.

EXAMPLE 2

The in vitro diffusion cell method described above was used to comparethe penetration of 30 microL of the commercial formulation Indospray™(Rhone-Poulenc Rorer, Australia), which is a 1.0% w/w solution ofindomethacin in 95% v/v ethanol when applied to the snake skin. 10microL of increasing concentrations of Octyl dimethyl PABA in absoluteethanol were applied 30 mins prior to the application of theindomethacin formulation. The control experiment involved application of10 microL of absolute ethanol alone 30 mins prior to the application ofthe indomethacin formulation. Samples were assayed according to themethod described previously. The detection wavelength was 254 nm and themobile phase consisted of acetonitrile:water (55% v/v:45% v/v) made topH 3·0 with orthophosphoric acid. Table 2 shows the mean flux ofindomethacin across the snake skin over 24 hours.

TABLE 2 Enhancer Mean flux +/− std p value Enhance- conc. error relativeto ment Enhancer type (% v/v) (microg.cm².h) control ratio Control - non/a 1.24 +/− 0.05 — — enhancer Octyl dimethyl 1.6 1.43 +/− 0.14 ns 1.2PABA as above, n = 3 3.2 1.71 +/− 0.32 ns 1.4 as above 6.4 1.94 +/− 0.090.0005 1.6 ns = not statistically significantly different

These results demonstrate the ability of the dermal penetrationenhancers to be applied alone prior to exposure of the skin to thephysiologically active ingredient(s) formulations without penetrationenhancers. Enhancement of percutaneous absorption is extensive, as wellas being dose-dependent in manner, such that the desired level ofenhancement can be achieved by utilising the appropriate dose of dermalpenetration enhancer applied to the skin.

EXAMPLE 3

The same protocol as Example 1 was repeated, except the dermalpenetration enhancers were included in the ketoprofen formulation, suchthat 400 microL of 2% w/v ketoprofen and 2% v/v dermal penetrationenhancer in 70% v/v aqueous ethanol was applied to the skin from thestart of the diffusion experiment.

Table 3 shows the mean flux of ketoprofen across the snake skin over 24hours. FIG. 3 shows the representative mean cumulative amount versustime plots for ketoprofen.

TABLE 3 Mean flux +/− p value relative Enhance- std error to mentEnhancer type (microg/cm².h) control ratio Control - no 0.78 ± 0.07 — —enhancer, n = 10 Azone, n = 2 2.84 ± 0.11 <0.0001 3.6 Octyl dimethyl2.71 ± 0.18 <0.0001 3.5 PABA, n = 2 Octylmethoxy 2.08 ± 0.39 0.0413 2.7cinnamate, n = 2 Octyl salicylate, n = 4 61.68 ± 14.89 <0.0059 79.1

These results demonstrate the ability of the dermal penetrationenhancers to be applied together with the physiologically activeingredient/s within the same formulation to achieve their percutaneousabsorption enhancement.

EXAMPLE 4

Table 4 shows the mean flux (% dose/h)+/−the standard error of the meanof hydroquinone (HQ) penetrated across full-thickness guinea pig skin invitro from a gel formulation applied to the skin at a dose of 15 mg/cm².Radiolabelled hydroquinone (C14, Amersham) was added to each of thetopical formulations. At specified time intervals 200 microL of receptorsolution was withdrawn with a micro-pipette and replaced with 200 microLof fresh normal saline. The 200 microL samples were added to 800 microLof water which in turn was added to 10 mL of scintillation cocktailconsisting of Toluene™ 1L, PPO 5g, POPOP 0.1 g and Triton X™ 500 mL. Thescintillation counting was performed on a Packard Tricarb 460Cinstrument. Disintegrations per minute were determined by an externalstandard procedure and calculated by the data system of the instrument.

TABLE 4 Enhancement ratio Flux (enhancer/ Enhancer type (% dose/h)control) PARSOL ® MCX 3% v/v 0.93 ± 0.19* 2.7 ESCALOL ® 507 3% v/v 1.02± 0.09* 2.9 AZONE 5% v/v,PARSOL ® MCX 1.48 ± 0.08* 43 3% v/v AZONE 5%v/v, ESCALOL ® 507 0.74 ± 0.02* 2.1 3% v/v PARSOL ® MCX 3% v/v, 1.30 ±0.10* 37 ESCALOL ® 507 3% v/v Control (no enhancer) 0.35 ± 0.10  — n >or = 10, * statistically significantly different from control, p <0.01following student t-test.

Table 5 shows the effect of hydroquinone (HQ) penetration acrossfull-thickness guinea pig skin in vivo on the mean melanin content(mg/cm²)+/−standard error of the mean following the application of afinite dose solution (5 microL/cm²). Melanin content was measured byreflectance absorbance from the treated and untreated skin according tothe methods outlined in the PhD thesis of Anderson, J. R., titled TheDevelopment of Techniques for Measuring the Bioavailability of TopicalDepigmenting Agents (School of Pharmaceutics, Victorian College ofPharmacy Ltd., Parkville, Victoria, Australia, Dec., 1985).

TABLE 5 Enhancement Melanin p value ratio content relative to (enhancer/HQ concentration/Enhancer type (μg/cm²) control control) HQ 1% w/vcontrol* 57.5 ± 3.7 — HQ 1% w/v, Octyl dimethyl 38.2 ± 3.1 0.002* 1.5PABA 2% v/v HQ 2% w/v control{circumflex over ( )} 36.8 ± 8.1 — HQ 2%w/v, Azone 2% v/v 39.5 ± 9.6 0.35{circumflex over ( )} 0.93 n = 8,Statistically significant differences tested for using a Student t-test.

EXAMPLE 5

Table 6 shows the median amount (μg/cm²) of ibuprofen penetrated acrossfull-thickness hairless mouse skin in vitro when 400 microL of a 2% w/vibuprofen and 2% v/v dermal penetration enhancer in 70% v/v aqueousethanol is applied. Again Azone was selected as the standard forcomparison and the control formulation contained no penetrationenhancer. The detection wavelength was 210 nm and the mobile phaseconsisted of acetonitrile:water (55:45) made to pH 3·0 withorthophosphoric acid.

TABLE 6 Enhancer type after 12 hours after 24 hours Octylmethoxycinnamate 2% v/v 1099* 2458* Octyl dimethyl PABA 2% v/v 1123*2981* Azone 2% v/v 1036* 2684* Control (no enhancer) 474  1819  n = 8, *statistically significantly different from control, p <0.05 followingANOVA on Ranks.

EXAMPLE 6

Table 7 shows the mean amount (μg/cm²)+/−standard error of the mean oftestosterone penetrated across dermatomed (300 μm thickness) neonateporcine skin in vitro when 10 microL of a 12% w/v testosterone and 8%v/v of dermal penetration enhancer in absolute ethanol was applied. Thedetection wavelength was 241 nm and the mobile phase consisted ofacetonitrile:water (55% :45%).

TABLE 7 Enhancer type after 4 hours after 24 hours Octyl dimethyl PABA8% v/v  72 ± 10* 227 ± 7* Control (no enhancer) 4 ± 1  13 ± 2*Enhancement ratio 18 17 n = 3, * statistically significantly differentfrom control, p <0.003 following Student t-test.

EXAMPLE 7

FIG. 4 shows the cumulative amount of ibuprofen transferred across shedsnake skin versus time for gel formulations of ibuprofen. 5 mg of eachgel was applied to the skin. Samples were assayed by the HPLC methodmentioned in Example 5. The gels were made to a final concentration of5% w/w ibuprofen and 2% w/w dermal penetration enhancer by firstdissolving them in 50% v/v aqueous ethanol then adding 2% w/w Sepigel305™ (SEPPIC, Paris, France) as a gelling agent and stirring at roomtemperature until a gel was formed. This formulation was compared withthe commercial IBUGEL™ (Dermal Laboratories, UK) formulation whichcontained 5% w/w ibuprofen in a ethanolic gel base formed with carbopol.As well, 2% w/w dermal penetration enhancer was added to the IBUGEL bysimple mixing. The ibuprofen contents of each gel were determined byHPLC and were found to be 5.02, 5.75 and 5.43 mg/g for the gel usingSepigel-305™ and enhancer, the IBUGEL and the IBUGEL with enhancer;respectively.

Both the cumulative amounts at 12 an 24 h and the mean flux over 24 hwere significantly greater (p<0.05) for both the enhanced gelformulations when compared to the commercial IBUGEL formulation. Theflux enhancement ratios were 6.15 and 2.61 for the gel usingSepigel-305™ and enhancer and the IBUGEL with enhancer (n=3)respectively when compared to the IBUGEL (p<0.05).

EXAMPLE 8

Table 8 shows the mean flux (g/cm².h) of hydrocortisone penetratedacross snake skin in vitro when 400 microL of 1% w/v hydrocortisone and2% v/v octyl dimethyl PABA in 70% v/v aqueous ethanol was applied. Thecontrol formulation contained no penetration enhancer. The detectionwavelength was 242 nm and the mobile phase consisted ofacetonitrile:water (35%:65%).

TABLE 8 Mean flux +/− std p value error relative to Enhancement Enhancertype (microg/cm².h) control ratio Control - no enhancer 0.14 +/− 0.04 —— Octyl dimethyl PABA 0.79 +/− 0.06 <0.0001 5.8 8% v/v

EXAMPLE 9

Table 9 shows the mean flux over 24 h of ketoprofen from a transdermalpatch using the enhancer octyl salicylate compared with a controlwithout enhancer. The patches were prepared by dissolving 300 mg ofketoprofen, 400 mg of penetration enhancer, 300 mg of polyethyleneglycol 400 and 800 mg of hydroxypropylcellulose in 20 mL of ethanol andstirring until viscous. This was then poured onto a clean glass plateand dried at 40 degrees Celsius for 1 h. The thickness of this film wasapproximately 1 mm. Circles of 0.8 cm² were then cut out of this matrixand stuck onto the middle of 2.0 cm² circles of OPSITE™ adhesivebandage. This patch was then stuck onto 2.0 cm² pieces of snake skin andplaced in the diffusion cell. The ketoprofen content of each patchformulation was determined by HPLC in triplicate and found to be6.99+/−0.30 mg/cm² and 6.76+/−0.24 mg/cm², for the control and octylsalicylate patches respectively (mean content+/−std error, n=4).

TABLE 9 Mean flux +/− std p value relative error to Enhancement Enhancertype (microg/cm².h) control ratio Control - 0.47 ± 0.04 — — no enhancerOctyl salicylate 11.70 ± 0.65  <0.0001 25.2

In order to further illustrate the present invention and the advantagesthereof, the following specific examples are given, it being understoodthat same are intended only as illustrative and in nowise limitative. Inthe examples, the effectiveness of the dermal penetration enhancers areillustrated by measuring the skin penetration of physiologically activeagents. Also, the skin penetration of the dermal penetration enhancersof this invention were compared with that of other penetration enhancersas well as formulations of bio-affecting agents with common adjuvants.The comparisons made generally consisted of measuring the relativepenetration through shed snake skin of the various formulations. In theexamples, the in vitro skin penetration studies were performed using thesame in vitro diffusion cell apparatus as previously mentioned.

EXAMPLE 10

FIG. 5 shows the mean cumulative amount of testosterone which crossesthe shed snake skin versus time.

The volume of each formulation applied to the skin was 5 microL/cm².Each formulation contained 12% w/v testosterone in absolute ethanol. Thedose was applied with a GC syringe. All except for the controlformulation had a penetration enhancer added at a concentration of 8%v/v.

Samples were assayed for testosterone by HPLC as shown before in Example6.

Table 10 shows the mean flux of testosterone over 24 h for each of theformulations and the degree of enhancement expressed as the ratio of themean flux of the penetration enhancer formulation divided by the meanflux of the control formulation.

TABLE 10 Mean flux +/− std p value relative Enhance- error to mentEnhancer type (microg/cm².h) control ratio Control - no enhancer 0.70+/− 0.03 — — Oleic acid 2.09 +/− 0.08 <0.0001 3.0 Azone 2.02 +/− 0.27<0.03 2.9 Octyl dimethyl PABA 1.43 +/− 0.25 <0.03 2.0 Octylsalicylate4.18 +/− 0.41 <0.03 6.0

EXAMPLE 11

Table 11 shows the mean flux over 24 h and the enhancement ratios for anumber of different preferred compounds after they are applied to theskin at a dose of 5 microL/cm². The two penetration enhancers given asexamples are octyl dimethyl PABA and Azone. Both penetration enhancerswere again at a concentration of 8% v/v within the formulations andcontrol was without a penetration enhancer. A concentration of 2% w/voestradiol was used in the formulation and detection wavelength was 212nm and the mobile phase consisted of acetonitrile:water (40%:60%). Aconcentration of 6% w/v progesterone was used in the formulation, thedetection wavelength was 240 nm and the mobile phase consisted ofacetonitrile:water (55%:45%). A concentration of 6% w/v norethisteroneacetate was used in the formulation, the detection wavelength was 240 nmand the mobile phase consisted of acetonitrile:water (55%:45%) adjustedto pH 3.0 with orthophosphoric acid. A concentration of 20% ibuprofenwas used in the formulation, the detection wavelength was 210 nm and themobile phase consisted of acetonitrile:water (55%:45%) adjusted to pH3.0 with orthophosphoric acid. A concentration of 20% flurbiprofen wasused in the formulation, the detection wavelength was 247 nm and themobile phase consisted of acetonitrile water (55%:45%) adjusted to pH3.0 with orthophosphoric acid.

TABLE 11 Mean flux +/− p value Enhance- std error cf. ment Drug Enhancertype (microg/cm² · h) control ratio Oestradiol Control, n = 3 0.06 +/−0.01 — — Azone 0.40 +/− 0.05 <0.003 6.4 Octyl dimethyl 0.26 +/− 0.01<0.0001 4.1 PABA Progesterone Control, n = 3 0.40 +/− 0.02 — — Azone, n= 3 2.17 +/− 0.33 <0.05 5.4 Octyl dimethyl 0.95 +/− 0.03 <0.0001 2.4PABA Norethisterone Control 0.14 +/− 0.02 — — acetate Azone 0.16 +/−0.02 <0.0001 1.1 Octyl dimethyl 1.85 +/− 0.07 <0.0001 12.8  PABAIbuprofen Control 5.39 +/− 0.50 — — Azone 13.53 +/− 1.38  0.0014 2.5Octyl dimethyl 13.16 +/− 1.21  0.001 2.4 PABA Flurbiprofen Control, n =3 0.81 +/− 0.05 — — Azone 2.05 +/− 0.42 0.0559 2.5 Octyl dimethyl 2.91+/− 0.30 0.0023 3.6 PABA, n = 3

The flux values obtained for these drugs are clinically relevant, givenfor example that in hormone replacement therapy for postmenopausal womenthe current transdermal delivery systems aim to provide 25 to 100 microgof estradiol per day and 250 microg of norethisterone per day(Estracombi™) and in testosterone replacement therapies the goal rangesfrom replacing 0.1 to 0.3 mg per day in women lacking testosterone (U.S.Pat. No. 5,460,820), to 5 to 6 mg per day in testosterone deficienthypogonadal men (Androderm™) and up to 6 to 10 mg per day for malecontraception (ref. J.Clin.Endocrinol.Metab., Vol. 81, 4113-4121, 1996).For the NSAIDs, ibuprofen and flurbiprofen increased drug flux isdesirably predicated on the basis that this will lead to higher localconcentrations of the active drug at the target site of pain andinflammation.

EXAMPLE 12

FIGS. 5 and 6 show the mean plasma levels of testosterone and oestradiolrespectively following application of the topical transdermal aerosols(described previously in examples 15 and 14 respectively) to domesticweanling pigs (7 to 8 weeks old) in vivo. Plasma testosterone andoestradiol levels were determined by high specificity radioimmunoassays,using commercially available assay kits. The oestradiol assay (OrionDiagnostica, Finland) was conducted according to the manufacturers'directions. The testosterone assay (Pantex, CAL, USA) was also conductedaccording to the directions, with the procedure modified to include anextraction step (90% diethylether/10% ethyl acetate) to remove anyspecies specific matrix effects. The control formulations were the sameaerosol systems as above, except they did not contain any dermalpenetration enhancer.

The male pigs receiving the testosterone dose were surgically castrated1 week prior to the commencement of the study to remove any interferencefrom endogenous testosterone production and at the same time a cephaliccannula was inserted to facilitate blood sampling. These procedures wereperformed under general anaesthetic halothane (Fluothane™).

The results shown are baseline subtracted, were the baselinetestosterone level at time zero was 4.3 nmol/L+/−1.1 nmol/L (mean+/−stderror mean) for the test group (n=4) and was <0.5 nmol/L for every pigin the control group (n=7). A single application of 9 sprays over 180cm² was applied at 9 am and blood samples were taken at the intervalsshown over 24 h. The mean body weight of the pigs were 19.9 kg+/−0.8 kgand 17.2 kg +/−0.4 kg for the test and control groups respectively. Thearea under the plasma concentration versus time curve (AUC) was 2.2 foldgreater (p<0.05) for the penetration enhancer formulation compared withcontrol. The calculated results for AUC were normalised to a body weightof 20 kg assuming volume of distribution is directly proportional tobody weight.

The male pigs receiving the oestradiol dose had baseline oestradiollevels of <0.02 nmol/L for every pig in the test group (n=4) and <0.02nmol/L for every pig in the control group (n=6). A single application of3 sprays over 30 cm² was applied at 9 am and blood samples were taken atthe intervals shown over 24 h. The mean body weights of the pigs were21.3 kg+/−1.0 kg and 17.5 kg+/−0.4 kg for the test and control grouprespectively. The area under the plasma versus time curve (AUC) was 14.1fold greater (p<0.0003) for the penetration enhancer formulationcompared with control. The calculated results for AUC were normalised toa body weight of 20 kg assuming volume of distribution is directlyproportional to body weight.

EXAMPLE 13

Male pigs were used as described above, and the testosterone spray wasapplied daily over 180 cm² as described previously. Once dailytestosterone application was performed at 9 am for 6 consecutive days,and on the sixth day blood samples were taken at the intervals shownover 24 h in FIG. 7. A baseline blood sample was taken at time=0 h, onday 1 and was 2.8 nmol/L+/−1.1 nmol/L (mean+/−std error mean), n=4. FIG.7 shows the mean plasma level of testosterone versus time over 24 h. Theresults shown are baseline testosterone subtracted and arerepresentative of the expected steady-state profile for testosterone.

FIG. 8 shows the mean cumulative amount of testosterone crossing thedomestic weanling pig skin in vivo, as determined by Wagner-Nelsonanalysis, which says that Flux=Plasma conc.×Clearance (Berner B., JohnV. A., Pharmacokinetic Characterisation of Transdermal Delivery Systems,Clin. Pharmacokinet., 26(2): 121-134, 1994.). Clearance was determinedprior to study commencement by a bolus dose of intravenous testosteroneand was found to be 663 ml/h.kg+/−139 ml/h.kg which was similar to thereported value for males of 655 ml/h.kg (Mazer N. A., Heiber W. E.,Moellmer J. F., Meikle A. W., Stringham J. D., Sanders S. W., Tolman K.G., Odell W. D., Enhanced transdermal delivery of testosterone: a newphysiological approach for androgen replacement in hypogonadal men, J.Control. Releas., 19, 347-362, 1992). Also included for comparison inFIG. 8 are the expected in vivo penetration across human skin and the invitro penetration of testosterone across shed snake skin. The in vivopenetration across human skin was based on a 2.2 fold lower permeabilityof testosterone in human skin compared with pig skin as determined invivo (Bartek M. J., LaBudde J., Maibach H. I., Skin Permeability InVivo: Comparison in Rat, Rabbit, Pig and Man, J. Invest. Dermatol.,58(3): 114-123, 1972);

FIG. 8 shows the controlled nature of testosterone penetration acrossthe skin in vivo, as well as the good predictive capability of the invitro shed snake skin diffusion model for ascertaining the likelypenetration of the testosterone across human skin. It is thereforeenvisaged that the flux values obtained in examples 10 and 11 will bevery similar to those obtained in humans in a clinical setting.

Further to this FIG. 9 depicts the predicted plasma levels oftestosterone in male subjects of a nominal weight of 70 kg based uponthe clearance value of testosterone in males shown above. For comparisonthe 95% confidence interval of the testosterone plasma level in normalhealthy adult males is given (Mazer, et al., J. Control. Releas., 19,347-362, 1992). As shown this delivery system is quite capable ofachieving the desired level of testosterone replacement in testosteronedeficient hypogonadal men based upon on simple once daily application ofthe delivery system.

Aerosol Device

A plastic-coated glass aerosol container of 10 ml fill volume was fittedwith a pharmaceutical grade metered-dose valve of a nominated dischargevolume (50 μl for the oestradiol aerosol and 100 μl for the testosteroneaerosol).

A stainless steel O-ring locks the valve in place on the aerosolcontainer.

The aerosol container is charged with at least one physiologicallyactive agent, non-volatile dermal penetration enhancer, volatile liquidcarrier and optionally any other diluents, carriers, surfactants oradditives followed by the propellant according to any suitable process.

A pharmaceutical grade spray nozzle and an aerosol shroud is fitted tokeep the spray nozzle perpendicular to the skin at a height of 50 mm.

Method of Aerosol Use

1. Hold the device upright in the palm of your preferred hand with yourthumb resting gently on the actuator button.

2. Rest the shroud opening on the skin and depress the actuator buttononce and release the button. Remove the device from the skin.

3. Repeat steps 1 and 2 on a new area of skin until the correct numberof doses have been given.

4. Allow the applied formulation to dry on the skin for 1 minute.

During application of the spray, the nozzle shroud envelopes the spray,providing an effective closed system which deposits the active agentinto the skin, and such that when the spray hits the surface of the skinit does not undergo any appreciable bounce-back into the atmosphere. Adefined dose of active agent and penetration enhancer is forced througha uniform spray nozzle at a constant pressure form a defined height togive a uniform dose per cm².

EXAMPLE 14

17-β-Oestradiol Metered-Dose Transdermal Aerosol Concentration Activeingredient: 17-β-Oestradiol  2% w/v Non-volatile dermal penetrationenhancer: Octyl dimethyl-para-aminobenzoate  8% v/v (Escalol 507,Padimate O) Volatile liquid: Absolute ethanol (AR) 60% v/v Volatilepropellant: Dimethyl ether 30% v/v to give a final formulation pressureof 2.0 kp/cm² (30 psi).

One spray of 50 μl will apply 1 mg of 17-β-oestradiol over an area ofapproximately 10 cm². 3 sprays will be administered to the forearm skin,applying a dose of 3 mg over approximately 30 cm².

EXAMPLE 15

Testosterone Metered-Dose Transdermal Aerosol Concentration Activeingredient: Testosterone 12% w/v Non-volatile dermal penetrationenhancer: Octyl dimethyl-para-aminobenzoate  8% v/v (Escalol 507,Padimate O) Volatile liquid: Absolute ethanol (AR) 50% v/v Volatilepropellant: Dimethyl ether 35% v/v to give a final formulation pressureof 2.4 kp/cm² (35 psi).

One spray of 100 μl will apply 12 mg of testosterone over an area ofapproximately 20 cm². 9 sprays will be administered to a defined area ofskin on the torso (rib cage), applying a dose of 108 mg overapproximately 180 cm².

EXAMPLE 16

Analgesic mousse with penetration enhancement Ingredient: ConcentrationIbuprofen   5% w/w 2-ethylhexyl-p-methoxycinnamate   5% w/w nonionicemulsifier  2.5% w/w ethyl alcohol (95%) 32.5% w/w purified water   50%w/w hydrocarbon propellant   5% w/w

Throughout this specification and the claims which follow, unless thecontext requires otherwise, the word “comprise”, or variations such as“comprises” or “comprising”, will be understood to imply the inclusionof a stated integer or group of integers but not the exclusion of anyother integer or group of integers.

What is claimed is:
 1. A non-occlusive percutaneous or non-occlusivetransdermal drug delivery system which comprises: (i) a therapeuticallyeffective amount of at least one physiologically active agent or prodrugthereof; (ii) at least one dermal penetration enhancer, which is presentin an amount of from 10 to 10,000 wt % based on the weight of the activeagent or prodrug thereof; (iii) at least one volatile liquid present inan amount to act as a vehicle for the active agent and penetrationenhancer; wherein: the dermal penetration enhancer (A) is adapted totransport the physiologically active agent across a dermal surface ormucosal membrane of an animal, when the volatile liquid evaporates, toform a reservoir or depot of a mixture comprising the penetrationenhancer and the physiologically active agent within said surface ormembrane, and (B) is of low toxicity to, and is tolerated by, the dermalsurface or mucosal membrane of the animal; and, after application of thesystem to an area of the dermal surface or mucosal membrane, the areabecomes touch-dry within 3 minutes of application.
 2. A drug deliverysystem according to claim 1, wherein said dermal penetration enhancer isone or more esters selected from the group consisting of C₈ to C₁₈ alkylpara-aminobenzoate, C₈ to C₁₈ alkyl dimethyl-para-aminobenzoate, C₈ toC₁₈ alkyl cinnamate, C₈ to C₁₈ alkyl methoxycinnamate and C₈ to C₁₈alkyl salicylate.
 3. A drug delivery system according to claim 1,wherein the drug delivery system is not supersaturated with respect tothe physiologically active agent.
 4. A drug delivery system according toclaim 1, wherein the dermal surface or mucosal membrane becomestouch-dry within 1 minute of application.
 5. A drug delivery systemaccording to claim 1, wherein the dermal penetration enhancer is a safeskin tolerant sunscreen.
 6. A drug delivery system according to claim 1,wherein said dermal penetration enhancer is an ester of formula (I):

wherein R¹ is hydrogen, lower alkyl, lower alkoxy, halide, hydroxy orNR³R⁴; R₂ is a long chain alkyl; R³ and R⁴ are each independentlyhydrogen, lower alkyl or R³ and R⁴ together with the nitrogen atom towhich they are attached form a 5- or 6-membered heterocyclic ring; n is0 or 1; and q is 1 or
 2. 7. A drug delivery system according to claim 1,wherein said dermal penetration enhancer is one or more esters selectedfrom the group consisting of a long chain alkyl para-aminobenzoate, longchain alkyl dimethyl-para-aminobenzoate, long chain alkyl cinnamate,long chain alkyl methoxycinnamate and long chain alkyl salicylate.
 8. Adrug delivery system according to claim 7, wherein said dermalpenetration enhancer is one or more esters selected from the groupconsisting of octyl dimethyl-para-aminobenzoate, octylpara-methoxycinnamate and octyl salicylate.
 9. A drug delivery systemaccording to claim 1, wherein the volatile liquid is ethanol orisopropanol.
 10. A drug delivery system according to claim 1, whereinthe physiologically active agent is a steroid, hormone derivative,non-steroidal anti-inflammatory drug, opioid analgesic, antinauseant,antioestrogen, aromatase inhibitor, 5-alpha reductase inhibitor,anxiolytic, prostaglandin, anti-viral drug, anti-migraine compound,antihypertensive agent, anti-malarial compound, bronchodilatar,anti-depressant, anti-Alzheimer's agent, neuroleptic and antipsychoticagent, anti-Parkinson's agent, anti-androgen or anorectic agent.
 11. Adrug delivery system according to claim 1, wherein the physiologicallyactive agent is testosterone, oestradiol, ethinyloestradiol,progesterone, norethisterone acetate, ibuprofen, ketoprofen,flurbiprofen, naproxen, diclofenac, fentanyl, buprenorphine,scopolamine, prochlorperazine, metochiopramide, ondansetron, tamoxifen,epitiostanol, exemestane, 4-hydroxy-androstenedione and its derivatives,finasteride, turostende, LY191704, MK-306, alprazolam, alprostadil,prostacylcin and its derivatives, melatonin, n-docosanol, tromantadine,lipophilic pro-drugs of acyclovir, low molecular weight heparin,enoxaparin, sumatriptan, amlodipine, nitrendipine, primaquine,minoxidil, minoxidil pro-drugs, pilocarpine, salbutamol, terbutaline,salmeterol, ibogaine, bupropian, rolipram, tacrine, fluphenazine,haloperidol, N-0923, cyproterone acetate or mazindol.
 12. A drugdelivery system according to claim 1, wherein the system is applied tothe dermal surface by an aerosol, as a spray.
 13. A drug delivery systemaccording to claim 12, wherein the aerosol is a fixed or variablemetered dose aerosol.
 14. A drug delivery system according to claim 1,further comprising a pharmaceutical compounding agent, co-solvent,surfactant, emulsifier, antioxidant, preservative, stabiliser, diluentor a mixture of two or more of said components.
 15. A method foradministering at least one systemic or locally acting physiologicallyactive agent or prodrug thereof to an animal which comprises applying aneffective amount of the physiologically active agent in the form of adrug delivery system according to claim 1 to a dermal surface or mucosalmembrane of said animal.
 16. A method for the treatment of a disease orcondition in an animal which comprises administering to a dermal surfaceor mucosal membrane of said animal in need of such treatment atherapeutically effective amount of the drug delivery system accordingto claim 1 to a dermal surface or mucosal membrane of said animal.
 17. Amethod according to claim 16, wherein the method is for the treatment ofa disease or condition selected from the group consisting of a diseaseor condition that requires male hormone replacement in testosteronedeficient hypogonadal men, a disease or condition that requires femalehormone replacement therapy for postmenopausal women, a disease orcondition that requires androgen replacement therapy for females lackinglibido, a soft tissue injury, narcotic withdrawal, severe post-operativepain, oestrogen dependent breast cancer, prostatic enlargement,prostatic cancer, alopecia, an anxiety disorder, male impotence,Raynaud's syndrome, varicose veins, a sleep disorder, herpes virusinfection, deep vein thrombosis, migraine, high blood pressure, andmalaria.
 18. A method according to claim 15, wherein the animal issuffering from or at risk of developing a disease or condition selectedfrom the group consisting of motion sickness, acne, jetlag, asthma andnocturnal asthma.
 19. A method according to claim 15, wherein the animalis a human.
 20. A transdermal drug delivery system according to claim 1,wherein the physiologically active agent or prodrug thereof, the dermalpenetration enhancer, and the volatile liquid are a single phase.
 21. Amethod according to claim 15, wherein the drug delivery system isapplied by an aerosol or spray comprising a shroud adapted to keep anactuator nozzle of the apparatus at a pre-determined height above thesite of application.
 22. A method according to claim 15, wherein theanimal is in need of male contraception or female contraception.
 23. Amethod according to claim 15, wherein the physiologically active agentor prodrug thereof is administered for the diagnosis of cystic fibrosis.